PlantFiles: Giant Horsetail
Equisetum telmateia

Actually I believe we have a smaller variety, Equisetum Arvense, but it seems to grow in any garden, wet or dry here and to be able to compete in the lawn. It is mercilessly invasive and though, I hear, useful in the herbal pharmacopia, it is the scourge of the garden. The roots are as brittle as the tops and likely impossible to completely eradicate by removal. I have heard that the only method of eradication is to change the soil pH, which I am investigating. Travels under sidewalks and porches to emerge on the other side.

This is possibly the worst weed in 2 of my hillside gardens. I thought it was pretty (at first) however, it is impossible to get rid of in moist soil, once it starts. I spend most of the summer pulling and repulling.

It grows by underground root (I believe) and the roots are so deep, and the plant itself so delicate above ground, that it will generally snap off before you can get it all. I have tried following the stem down as far as possible, but without digging up the entire garden (unrealistic), once you have it, you'll probably always have it.

It only seems to thrive in soil that stays moist year round. Since we have springs in the aforementioned gardens, that is the case. It doesn't seem to be a problem in my other gardens, which have well drained soil that will normally dry out and have to be watered.

These plants grow in the few damp places on my land here in SW France. They are also common in the local ditches and other damp spots. Although they have the reputation for being invasive, the summer is so hot and dry here that they are pretty well confined to small areas.
I find them very attractive as they are feathery and a fresh green.